Chapter 8 Blood and Blood Spatter lets complete

Chapter 8 Blood and Blood Spatter …let’s complete a couple more case studies before we discuss blood! By the end of this unit you will be able to: l explain the composition of blood l describe the function of blood cells l determine the blood type of a blood sample l conduct a blood spatter analysis l examine wounds and describe the nature of the weapon l find and process blood evidence All Rights Reserved South-Western / Cengage Learning © 2009 1 Forensic Science: Fundamentals & Investigations, Chapter 8

Introduction and History Blood typing can provide class evidence; whereas DNA profiling can provide individual evidence. l A blood spattern can give information about the truthfulness of an account by a witness or a suspect. l It also can provide information about the origin of the blood, the angle and velocity of impact, and type of weapon used. l Our understanding of blood began in ancient times and continues to grow today. l 2 Forensic Science: Fundamentals & Investigations, Chapter 8

This is Dr. Henry Lee, the world’s leading serologist specialist. He has been involved with over six thousand cases within the past forty years. Serologists are people who study blood in a forensics laboratory. 3 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Detection…see activity 8. 1 l Phenolphthalein l Luminol 4 Forensic Science: Fundamentals & Investigations, Chapter 8

Transferred blood Footprint 5 Forensic Science: Fundamentals & Investigations, Chapter 8 Handprint

Luminol is a chemical that reacts with the hemoglobin in the blood to produce a blue luminescence. Luminol is used by investigators when the blood is wiped away and is therefore no longer visible to the naked eye. The brighter and stronger the glow, the more recent (and fresh) the blood is. The brighter and stronger the glow, the more heavy the blood flow. 6 Forensic Science: Fundamentals & Investigations, Chapter 8

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Composition of Blood l Whole blood carries cells and plasma—the fluid 9 with hormones, clotting factors, and nutrients. Shown above respectively: l Red blood cells carry oxygen to the body’s cells and carbon dioxide away. l White blood cells fight disease and foreign invaders and, alone, contain cell nuclei. l Platelets aid in blood clotting and the repair of damaged blood vessels. Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Typing—Proteins 42% 12% 3% of the population in the United States (of which 85% is Rh+) Blood typing is quicker and less expensive than DNA profiling. l It produces class evidence but can still link a suspect to a crime scene or exclude a suspect. l 10 43% Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Typing—Antibodies; Additional Proteins and Enzymes l Antibodies are proteins secreted by white blood cells that attach to antigens to destroy them. l Antigens are foreign molecules or cells that react to antibodies. l Enzymes are complex proteins that catalyze different biochemical reactions. l Many enzymes and proteins have been found in the blood that are important for identification purposes. 11 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Typing—Probability and Blood Types l Given the frequency of different genes within a population, it is possible to determine the probability that a particular blood type will appear in a particular population. l To determine the probability of two separate events, it is necessary to multiply their individual probabilities. l By identifying the additional proteins in the blood evidence sample, investigators can limit the size of a suspect population and help identify a suspect. 12 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter In 1939 the meaning of the spattern was first analyzed. l When a wound is inflicted, a blood spattern may be created. l It takes a grouping of blood stains to make a blood spattern. l The pattern can help to reconstruct the events surrounding a shooting, stabbing, or beating. l 13 Forensic Science: Fundamentals & Investigations, Chapter 8

Why study Blood Spatter? ◊ To find out where an assault occurred ◊ To find out the position of the killer during the attack ◊ To find out if the victim was walking or running during the attack ◊ To find out if victims tried to avoid the blows, by holding up object or arms to avoid the hits. (There would be a gap in the spatter if this happened. ) ◊ To find out the type of blood for victim or suspect identification 14 ◊ To find out how long the blood has been there to find a time frame for the attacks Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Splatter Analysis of a spattern can aid in determining the: – direction blood traveled. – angle of impact. – point of origin of the blood. – velocity of the blood. – manner of death. 15 Forensic Science: Fundamentals & Investigations, Chapter 8

Simpson Crime Scene 16 Forensic Science: Fundamentals & Investigations, Chapter 8

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Does blood spatter evidence consistent with the story told by witness or suspect? 19 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis l When blood falls from a height or at a high velocity, it can overcome its natural cohesiveness and form satellite droplets. l When it falls onto a less-than-smooth surface, it can form spiking patterns around the drops. 20 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis—Six Patterns 21 Describe each of these: a. passive drops b. arterial gushes c. splashes d. smears e. trails f. pools Forensic Science: Fundamentals & Investigations, Chapter 8

Arterial Gush 22 Forensic Science: Fundamentals & Investigations, Chapter 8

Arterial Spurting (or Gushing) Pattern Bloodstain pattern that results from blood exiting the body under pressure from a breached artery. The blood gushes out with the rhythm of the heart. Cast off pattern- Created when blood is released or thrown from a blood bearing object in motion (for example a knife). These are also called cast-off stains. 23 Forensic Science: Fundamentals & Investigations, Chapter 8

Drip Pattern- A blood stain pattern which results from dripped blood either from a weapon, victim or sometimes the killer. Flow pattern- A blood stain pattern which shows a change in shape and direction due to gravity or other forces. 24 Forensic Science: Fundamentals & Investigations, Chapter 8

Swipe pattern- this pattern is created when blood is transferred from a moving source onto an unstained surface. Contact Patterns. These types of patterns occur when a wet or bloody surface comes into contact with a second surface. 25 Forensic Science: Fundamentals & Investigations, Chapter 8

This type of stain can tell how many times a person was hit. The number of stains is always one less than the number of hits, because the first time the weapon hits there is no blood on it. 26 Forensic Science: Fundamentals & Investigations, Chapter 8

Types of Injury 27 l High velocity (gunshot) l Medium velocity (hammer strike) l Low velocity ( drip) Forensic Science: Fundamentals & Investigations, Chapter 8

Hammer strike-low velocity 28 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis—Impact Patterns can help investigators determine the type of weapon used. – What kind of a pattern is produced by a gun shot? – 29 What kind of a pattern is produced by a hammer blow? Forensic Science: Fundamentals & Investigations, Chapter 8

Surfaces If the surface is more rough and porous, the spatter will be absorbed. This picture shows the blood spatter on a carpet. If the surface is hard, smooth and flat, like tile, the spatter will break up into lots of little drops, and they will be round. This picture shows a close up of one of the drops. 30 Forensic Science: Fundamentals & Investigations, Chapter 8

31 The greater the height, the greater the amount of spatter. Forensic Science: Fundamentals & Investigations, Chapter 8

A blood drop falling perpendicular onto a surface (at a 90º angle) will leave a round blood stain where it drops. A blood drop falling at an angle other than 90º will leave an elongated stain. The steeper the angle, the more elongated the blood stain. 32 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis— Directionality The shape of an individual drop of blood provides clues to the direction from where the blood originated. How will the point of impact compare with the rest of a blood pattern? 33 Forensic Science: Fundamentals & Investigations, Chapter 8

The tail of the spatter tells us the direction the blood spatter came from. 34 Forensic Science: Fundamentals & Investigations, Chapter 8

Blood Spatter Analysis—Location of the Origin of the Blood l l 35 Lines of convergence Draw straight lines down the axis of the blood splatters. Where the lines converge, the blood originated. Forensic Science: Fundamentals & Investigations, Chapter 8

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Points of Convergence 37 The red circle shoes the point of convergence. Forensic Science: Fundamentals & Investigations, Chapter 8

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Crime scene 39 Forensic Science: Fundamentals & Investigations, Chapter 8

Crime scene 40 Forensic Science: Fundamentals & Investigations, Chapter 8

Reconstruction of crime scene 41 Forensic Science: Fundamentals & Investigations, Chapter 8

One of Bundy’s victims 42 Forensic Science: Fundamentals & Investigations, Chapter 8

Sharon Tate crime scene 43 Forensic Science: Fundamentals & Investigations, Chapter 8

Ron Goldman 44 Forensic Science: Fundamentals & Investigations, Chapter 8

Crime Scene Investigation of Blood 1. Search for blood evidence. 2. If any is discovered, process it determining: a. Whether the evidence is blood. b. Whether the blood is human. c. The blood type. 3. Interpret the findings: a. See if the blood type matches a suspect. b. If it does not, exclude that suspect. c. If it does, decide if DNA profiling is needed. 45 Forensic Science: Fundamentals & Investigations, Chapter 8

. . . . Summary l Blood consists of cellular components and plasma. l The various human blood types are caused by the presence or absence of A or B or both A and B proteins on the surface of red blood cells. l Blood spatter evidence can be used to recreate a crime scene. l Investigators endeavor to (a) locate, (b) identify, and (c) interpret blood splatter patterns at crime scenes. l Blood patterns will help determine the weapon, direction and location of impact. 46 Forensic Science: Fundamentals & Investigations, Chapter 8